March 29, 2007

 

South-west Australian wheat faces long-term warming, drying trend
 

 

South-west Australia, one of the world's major sources of traded wheat, faces long-term drying and warming, a trend now partly attributable to increases in greenhouse gases, according to a statement issued Thursday by Australia's premier science agency, the Commonwealth Scientific Industrial Research Organization, or Cairo.

 

By 2030, temperatures in the south-west will rise in all seasons, Bryan Bates, a senior Cairo marine and atmospheric research scientist, said in the statement.

 

"Rainfall may decline by as much as 20 percent relative to the 1960-1990 level, with the number of winter rain days decreasing by up to 17 percent and runoff in south-west catchments consequently decreasing by between 5 percent and 40 percent," he said.

 

"By about 2085, these changes may further increase, with rainfall declining by between 5 percent and 34 percent and the number of winter rain days decreasing by up to 30 percent," he said.

 

Wheat production in the south-west peaked at 11.1 million tonnes in 2003/04, but under the influence of a severe drought in 2006, slumped to 5.0 million tonnes this crop year ending Mar 31, 2007.

 

With only a small domestic market in Australia's south-west, nearly all the wheat produced is available for export to a global traded market estimated in 2006 at about 106 million tonnes.

 

Large quantities of barley, canola and lupins have also been produced and exported from the region.

 

Crops in the area typically rely on winter rains in the period June through mid-September to get through to harvest in November and December.

 

A parallel long-term trend in the region is for farmers to adopt technology and agronomic practices that enable better use of available moisture.

 

Cairo is part of a research team that also partners the Western Australian government and the federal Bureau of Meteorology.

 

Pandora Hope, of the Bureau of Meteorology, said research results provide increased confidence in the causes of recent past climate changes in the south-west.

 

A sudden decline in south-west early winter rainfall that began in the 1970s is occurring because the potential for storm development over this region has decreased due to much weaker winds in the upper atmosphere, she said.

 

Since the mid-1970s, there has been a decrease in the number of winter weather systems that bring wet conditions to the south-west and an increase in the number of systems that bring dry conditions.

 

"The observed rainfall decline in the south-west is likely to have been caused by both natural fluctuations and increases in greenhouse gas concentrations," Hope said.

 

The next phase of research will further investigate how much of this change might be explained by natural variations in the climate or if this is a consequence of human activity, she added.